Local treatment method for a conductive element, device for implementing it and conductive element.

Abstract

TITLE: Method for local treatment of a conductive element, device for implementing it, and conductive element. The invention relates to a method for treating a local portion (21) of a conductive element (2) comprising: mounting a tubular device (1) around the conductive element (2), the device comprising a heating section (12) axially adjacent, at its ends, to two cooling sections (13, 14), the heating section (12) covering said local portion (21); heating said heating section (12) to reach a setpoint temperature determined according to the following formula: , Tm being the melting temperature of the conductive material, A and B being linear functions of R; maintaining said setpoint temperature Tf for a heating period; ceasing the heating; holding the device (1) in place so that the cooling sections (13, 14) cool the local portion of the conductive element. Figure 6

Description

Title of the invention: Method for local treatment of a conductive element, device for implementing it and conductive element. technical field

[0001] The scope of this disclosure is that of electrical distribution, in particular on board aircraft. Previous technique

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses both on new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and lighter on-board equipment, but also on the development of the use of electrical technologies to provide propulsion.

[0006] In this context, the increasing development of aircraft electrification requires the installation of electrical distribution equipment in increasingly constrained environments, whether in terms of space or operating temperature.

[0007] To ensure this distribution, two main conducting elements stand out: - Harnesses: These are wire harnesses made up of various components that allow both the transmission of power required for the operation of equipment or loads, and the protection of the cable and its environment (equipment, structure, people, etc.). A harness consists of a conductive core, one or more layers of insulation, and possibly a screen / shield. It may also include other components such as a filler sheath and an armor / over-shield. In aeronautics, the cores are often called "multi-strand" because they can be made up of helical layers of twisted strands. A strand is a cylindrical component with a uniform cross-section, obtained by drawing a semi-finished product, then a rough wire. Different types of strands and different assembly and compaction techniques (passing the conductor through a die) are used to obtain a conductor that meets the desired performance requirements.For electrical distribution in aircraft, two materials are mainly used: "ETP" (Electrolytic Tough-Pitch) copper, characterized by a minimum copper content of 99.9%, or low-alloy aluminum (1XXX series). Busbars: These are rigid electrical connection components, primarily made from "ETP" copper or low-alloy aluminum alloys (1XXX series, typically 1350, 1370, or 6061) due to their excellent electrical properties. These bars are produced by machining a semi-finished product, which itself usually (most often) results from continuous casting followed by rolling.

[0008] Given the increasing power required to supply propulsion engines, improving the electrical conductivity of the aforementioned components is essential to limit the mass carried on board aircraft. This is all the more important since the highly congested environment in which they are mounted necessitates bending these conductive elements in numerous places. However, bending a conductive material tends to locally increase its resistivity and locally decrease its electrical conductivity due to structural defects, microcracks, work hardening, and changes in cross-section that it can generate. High resistivity of a material leads to its heating by Joule heating, which poses significant design constraints: there is a growing need to limit the intensity of the currents flowing through it to prevent degradation. polymers constituting the insulators, and increasing the conductive sections (due to microstructural modifications of the conductive material, and therefore its mechanical or electrical performance), which negatively impacts the mass and size of the aircraft.

[0009] To overcome these problems, it is known to manufacture conductors in such a way as to promote a particular microstructure, notably a single-crystal or coarse-grained oriented structure, which improves electrical conductivity and mitigates the problems mentioned above. Without being bound by theory, single-crystal or coarse-grained oriented structures are less prone to an increase in resistivity when the conductor is bent, because their composition is more homogeneous, exhibiting fewer grain boundaries. Processes for promoting the formation of such microstructures during conductor manufacturing have been developed and are described below.

[0010] The "Ohno Continuous Cast" (OCC) method is well known. This continuous casting process is used, in particular, to produce copper and silver wires with a high-purity crystalline structure and very few defects. This method is distinguished by its ability to create wires with larger and more homogeneous crystals, which improves the electrical properties of the material. Unlike traditional methods where the metal solidifies rapidly and unevenly, the OCC method allows for controlled cooling and solidification. This promotes the formation of large crystals or metal grains. Indeed, heating the mold walls and varying the rate of molten bath withdrawal create a solidification front perpendicular to the wire axis, thus generating a uniform crystalline orientation.This process makes it possible to obtain materials whose structure is solidified in a quasi-directional manner, although grain boundaries persist, unlike single-crystal materials.

[0011] The so-called "Czochralski process," which allows the production of large single-crystal materials, is also known. The process consists of heating the material to be crystallized just above its melting point in a crucible, with a controlled temperature gradient for directed solidification. A single-crystal seed is slowly immersed and withdrawn from the molten bath while being slowly rotated to ensure uniform crystal growth. This process, known as "epitaxy," allows the crystal to grow while maintaining its single-crystal structure. The operation can preferably be carried out under a neutral atmosphere to avoid oxidation.

[0012] In addition, the so-called "zone melting" process is also known, which consists of slowly pulling a rod or wire through a localized heating zone, melting the material locally. Surface tension creates a meniscus of liquid material between the feed and the withdrawn rod, allowing the single crystal to solidify thanks to A thermal gradient perpendicular to the rod axis is used. Sealed quartz tubes and a polymer coating can be used to hold the wires in position during melting. The second advantage of such a coating is to extend the material's solidification range. Indeed, the solidification window of pure copper is very narrow (liquidus = 1083°C and solidus = 1065°C), making meniscus control very difficult. The coating creates a kind of shell that contains the molten metal, thus allowing easier directional solidification. Argon can be introduced to prevent oxidation. Controlling residual porosity is crucial, and hot isostatic pressing (HIP) can improve electrical conductivity. This process is suitable for manufacturing single-crystal wires and busbars.

[0013] In summary, these different methods make it possible to produce single-crystal or coarse-grained oriented materials. The advantage of such materials is that they offer improved electrical conductivity: up to 105% IACS can be achieved with the "OCC" method and 117% IACS with the Czochralski method (IACS is a reference used to evaluate the relative electrical conductivity of materials compared to that of pure annealed copper). These performance levels are explained by the near absence of grain boundaries, which act as barriers to electrons, thus increasing resistivity.

[0014] However, the mechanical properties of the materials obtained are lower than those of the original material. These methods are manufacturing processes that affect the entire length of the wire or bar obtained, and result in a deterioration of the mechanical strength of the entire conductive element.

[0015] The purpose of this disclosure is therefore to mitigate at least in part the disadvantages of the prior art mentioned above. Summary

[0016] The objectives mentioned above are achieved in particular by a process for treating a local portion of an electrically conductive element made of a conductive material, the process comprising the steps of: - to mount a device around the conducting element, the device comprising a tubular body with axis X and radial thickness E, having a passage of equivalent radius R configured to accommodate the conducting element, the device comprising a heating section being axially adjacent, at its ends, to two respective cooling sections, the heating section extending axially over a length Le and the two cooling sections each extending axially over a length Lf, the heating section comprising a heating element, the cooling sections each comprising a cooling system, the the device being mounted so that the heating section covers said local portion of the conductive element, - heat said heating section by the heating element until it reaches a setpoint temperature determined according to the following formula: _ .vin(i+^) , Tm being the melting temperature of the conductive material, A and f = ” B+L' / z +1 m where B are linear functions of R, and the temperature Tf is expressed with a margin of error of + / - 5%, - maintain said setpoint temperature Tf for a determined heating period, - stop heating the heating element, and - maintain the device in place so that the cooling portions cool the local portion of the conductive element so that it returns to ambient temperature.

[0017] Thus, the conductive element is not manufactured in a particular way, as is the case in the prior art, but is treated afterward and only over a portion of its length. Indeed, this process makes it possible to locally treat a conductive element so that it obtains a single-crystal or coarse-grained oriented microstructure, for example, over a portion representing less than 50% of its total length. This makes it possible to obtain a conductive element exhibiting, locally: - exceptional folding capacity, thus meeting the needs of the constrained environment in which they are installed, - increased electrical conductivity, which helps to limit the loss of conductivity due to folding.

[0018] Furthermore, the process allows the conducting element to retain satisfactory mechanical properties over the rest of its length, which is not intended to be bent.

[0019] Consequently, such a process makes it possible to significantly improve the energy efficiency of aircraft and, in this sense, contributes to reducing their environmental impact.

[0020] The features described in the following paragraphs may optionally be implemented independently of each other or in combination with each other:

[0021] According to an improvement, A is a*R+b, with a between 270 and 300, preferably 285, and b between -0.7 and -0.5, preferably -0.6; and / or B is a'*R+b' with a' between 1.0 and 1.2, preferably 1.1 and b' between -0.0020 and -0.0018, preferably -0.0019.

[0022] According to an improvement, the temperature maintenance step extends for a period of between 8 and 12 minutes, preferably 10 minutes.

[0023] This disclosure also relates to a device capable of implementing the method as previously described, the device comprising a tubular body of axis X, having a passage configured to accommodate the conductive element, the device comprising a heating section being axially adjacent, at its ends, to two respective cooling sections, the heating section comprising a heating element, the cooling sections comprising a cooling system.

[0024] According to an improvement, the tubular body has a radial thickness E, the passage has an equivalent radius R, the heating section extends axially over a length Le and the two cooling sections each extend axially over a length Lf, the device being dimensioned in such a way that at least one of the following three criteria is met: LC<4*R; 0.001m < E < 0.01m; - and that Lf > 0.01m.

[0025] According to an improvement, the tubular body or each of the sections (in particular in the case where the tubular body is formed of several sections assembled together) comprising two half-cylinders linked together by an articulation system so that the device is configured to close around a local portion of said conducting element.

[0026] According to an improvement, the heating element and / or the cooling system are located on a radially external side respectively of the heating section and the cooling sections.

[0027] According to an improvement, the heating element comprises one of the following: a coil, a resistor.

[0028] According to an improvement, the heating section comprises one of the following materials: alumina, ceramic.

[0029] According to an improvement, the cooling system includes a water circulation.

[0030] According to an improvement, each cooling section comprises steel.

[0031] According to an improvement, the heating section is a first heating section and the two cooling sections constitute a first cooling section and a second cooling section, the device further comprising a second heating section being axially adjacent, to its ends, to the second cooling section and to a third cooling section respectively.

[0032] According to an improvement, the second cooling section extends axially over a length Lf2 dimensioned such that Lj-^ > 0.03œ.

[0033] This disclosure also relates to an electrically conductive element comprising at least a local portion treated by the treatment process as described above.

[0034] This disclosure also relates to a conductive element, preferably treated by the process described above, extending over a length L along an elongation direction and comprising: - a treated local portion comprising a first single-crystal or coarse-grained microstructure in which the grain(s) are directed along the elongation direction X of the conducting element, the local portion comprising a maximum of 20 grains per conductor cross-section considered at any point perpendicular to the elongation direction X of the length of the local portion, - an untreated portion distinct from the treated portion and comprising a polycrystalline microstructure in which the grains are randomly oriented, the untreated portion comprising at least 21 grains per conductor cross-section considered at any point perpendicular to the elongation direction X of the length of the untreated portion Brief description of the drawings

[0035] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0036] [Fig-1] shows two types of conductive elements given as non-examples limiting factors, including, in particular, a busbar with two folding zones shown in view 1a, and in view 1b, a conductor of the multi-strand harness type,

[0037] [Fig.2] shows a schematic perspective view of an example of a device suitable for implementing the process according to this disclosure,

[0038] [Fig.3] shows a longitudinal cross-sectional view of a device according to [Fig.2] when mounted on a conductive element according to an example,

[0039] [Fig.4] shows a longitudinal cross-sectional view of a device according to a second example, which comprises several heating sections, when mounted on a conductive element according to an example,

[0040] [Fig. 5] shows two cross-sectional views 5a and 5b of two examples of devices which are distinguished in particular by the shape of their sections,

[0041] [Fig. 6] shows a longitudinal cross-sectional view of a device mounted on an element conductor according to an example, on which the treated portion and the solidification fronts obtained according to the treatment process are particularly visible,

[0042] [Fig.7] shows several sets of points, each obtained for an element conductor of a specific diameter, each point cloud showing configurations allowing satisfactory process efficiency according to this disclosure, the points are illustrated with a margin of error of approximately + / -5%,

[0043] [Fig.8] shows a perspective view of a conducting element according to an example and of two cross-sectional planes PI and P2 considered respectively at the level of a treated portion and an untreated portion of the conductor,

[0044] [Fig.9] shows two cross-sectional views 9a and 9b corresponding to examples of microstructures that can be obtained at the respective levels of the PI and P2 section planes shown in [Fig.8],

[0045] [Fig. 10] shows a perspective and transparency view of the microstructure example shown in view 9a of [Fig.9], on which the orientation of the large grains is particularly visible. Description of the implementation methods

[0046] The drawings and description below contain, essentially, elements of a definite nature. They may therefore not only serve to better understand this disclosure, but also contribute to its definition, if necessary.

[0047] In the various figures, the same reference numerals designate identical or similar elements. For the sake of brevity, only the elements that are useful for understanding the described embodiment are shown in the figures and are described in detail below.

[0048] In the following description, when reference is made to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientational qualifiers, such as "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0049] As described above, the present disclosure aims to propose a method for treating a local portion of an electrically conductive element. Two main types of conductive elements are considered in particular: the busbar and the harness, two examples of which are shown respectively in views 1a and 1b of [Fig. 1]. These two elements are generally elongated and differ mainly in their cross-section. Indeed, the busbar has a polygonal, typically rectangular, cross-section, while the harness has a typically circular cross-section.

[0050] These different conductors can also be distinguished by their composition: the busbar typically comprises a single-piece bar, while the harness can be composed of several strands 216 twisted together to form a conductive core 215. In both cases, the conductive element may include protective elements 217 such as a sheath, armor, and / or insulation. In the application of the process described below, it is possible, in particular, to pre-remove this protective element 217 in order to process the conductive core or the bar alone.

[0051] Only these two types of conductors are described in detail, but it is also possible to consider any other type of conductive element without departing from the scope of this disclosure.

[0052] By way of example, the process according to this disclosure can also be used for repair or strand-by-strand joining. Indeed, it is possible to take advantage of the fusion operation to join two conductive elements, whether of the same or different types. Therefore, according to this process, it is possible to perform both a processing operation and an joining operation on the two ends of two separate conductive elements.

[0053] By way of example, the busbar shown in view of [Fig. 1] has two bend zones Zp necessary for its integration into its mounting environment. It is typically this type of bend zone Zp that can be usefully processed according to the method of this disclosure.

[0054] Reference is now made to [Fig.2], which shows an example of device 1 suitable for implementing the treatment process according to this disclosure.

[0055] The device 1 comprises a tubular body extending along a longitudinal direction X. The tubular body is shown here with a general cylindrical shape of revolution, but it is also possible for the tubular body to have a polygonal cross-section, for example, rectangular. In general, it may be advantageous to provide a cross-section of the device (circular, polygonal, asymmetrical, etc.) that corresponds homothetically to the cross-section of the conductor to be treated, for reasons of energy efficiency of the treatment.

[0056] Furthermore, the tubular body includes a passage 11. The passage 11 extends along the entire length of the tubular body and opens at each of the two ends 113, 114 of the tubular body. Such a passage has, in particular, the function of receiving the local portion 21 of the conductive element that is to be treated.

[0057] The passage 11 is delimited by an internal surface 111. The internal surface 111 is shaped so that the passage 11 has a circular, oval, or polygonal cross-section, for example, a rectangular one. It will be understood, in particular, that a rectangular passage 11 is especially suitable for processing a busbar of the type shown in Figure 1a, whereas a rectangular passage 11 The circular section is particularly suitable for processing a harness of the type shown in Figure 1b. It is also possible to adapt passage 11 for other types of conductive elements.

[0058] Advantageously, the passage 11 can have a cross-section of constant shape and size over the entire length of the tubular body of the device 1.

[0059] According to the examples shown in Figures 2 and 3, the tubular body of the device 1 comprises two cooling sections 13, 14 and a heating section 12. More generally, the tubular body of the device 1 may comprise one or more heating sections, and as many cooling sections as necessary so that each heating section is axially adjacent to two cooling sections. By "adjacent," it should be understood that each cooling section is contiguous with, or directly in contact with, the heating section. Optionally, a slight mounting clearance or positioning error may be tolerated, for example, on the order of less than 10% of the axial length of the heating section. The various sections are coaxial with the X-axis.

[0060] As shown in [Fig.2] and 3, the heating and cooling sections represent sections of the tubular body which are stacked in the following order: a first cooling section 13, the heating section 12, then a second cooling section 14.

[0061] According to examples, a system of chutes can be provided at the interfaces between the heating section 12 and the cooling sections 13, 14 allowing the assembly to be centered.

[0062] According to examples, the heating sections 12 and cooling sections 13, 14 each have an identical cross-section.

[0063] Another embodiment of the device is shown in [Fig. 4]. In this example, the tubular body comprises two heating sections 12, each axially adjacent to two cooling sections, the central cooling section 13.2 being common to both heating sections. This results in three cooling sections 13.1, 13.2, and 13.3 for two heating sections 12.1 and 12.2.

[0064] This disclosure is therefore not limited to a single heating section; the described device can be equipped with several heating sections, particularly if it is useful to treat several local portions of the conductive element, for example, to bend it in several places. A device with any number of heating sections can be obtained by extrapolating the configuration shown in [Fig. 4], by adding, following an end cooling section, a heating section and then another cooling section, and so on, alternately.

[0065] Again in relation to [Fig.3], the heating section 12 can be functionally linked to a heating element 31, so that the heating element 31 can be configured to raise the temperature of the heating section 12. Similarly, the cooling sections 13, 14 are functionally linked to a cooling system 32, configured to lower the temperature of the cooling sections, or to prevent them from heating above a maximum temperature.

[0066] According to examples, the heating element 31 may include a coil for achieving magnetic induction heating, and / or include a resistance capable of generating heat by Joule effect.

[0067] In some examples, the cooling system 32 may include a circulation of cooling fluid (e.g., water or gas) suitable for removing heat from the cooling sections 13, 14. In some examples, air cooling may be sufficient. A pump, a heat exchanger, a fan, and / or a thermostat (not shown) may be provided to carry out the circulation of the cooling fluid.

[0068] Of course, other types of heating or cooling systems known to a person skilled in the art may be considered.

[0069] The heating element 31 can be controlled by a processor linked to a thermocouple capable of measuring the temperature at the local portion 21 of the conductive element 2, in order to control in a closed loop the supply of heat to the local portion 21.

[0070] The heating section 12 is configured to allow homogeneous conduction of heat to the local portion 21 of the conducting element 2. Indeed, the heating section 12 can have a volume that is uniformly distributed around the conducting element 2. In particular, it can be provided that the quantity of material of the heating section that surrounds the conducting element has a constant radial dimension.

[0071] Furthermore, the heating section 12 may comprise a material suitable for very high temperatures, for example ceramic or alumina. The cooling sections 13, 14, on the other hand, may be made of a metallic material with good thermal conductivity, for example steel.

[0072] The respective dimensions of the cooling and heating sections are particularly visible in Figures 2, 3, and 4. In the case illustrated in [Fig. 2] and 3, where the device has only one heating section 12, the cooling sections 13 and 14 can extend over the same length Lf. In other examples, the lengths of the cooling sections may be different.

[0073] In the case where the device comprises several heating sections, for example two heating sections 12.1, 12.2 as illustrated in [Fig. 4], the "central" cooling section 13.2 may extend over a length Lf2 different from the other two cooling sections 13.1, 13.3 of length Lf. The heating section 12, for its part, extends over the length necessary to cover the local portion 21 to be treated. For simplicity, the heating sections are assumed to be of the same length Le, but it is possible to provide different lengths if the local portions 21.1, 21.2 to be treated are of different lengths.

[0074] Generally, the local portion 21 is intended to be subsequently folded to facilitate the integration of the conductive element 2 into the aircraft. The local portion 21 can therefore typically be delimited by two substantially straight portions of the conductive element 2. Consequently, the local portion 21 may, for example, extend over a length less than 50% of the length of the conductive element. According to some examples, the local portion 21 can be considered distinct from the ends of the conductive element 2.

[0075] Furthermore, the tubular body of the device also has the following main dimensions: - A radial thickness E, corresponding to the dimension, along a radial direction, between the internal surface 111 of the passage 11 and an external surface 112 of the tubular body of the device. - A passage with an equivalent radius R equal to the equivalent radius of the conductor, the radius is called "equivalent" because for passages and conductors with non-circular cross-sections, it will be equal to the value of a theoretical radius that would give the same cross-sectional area: where A is the area of ​​the cross-section. driver.

[0076] Having described device 1, we will now develop the different steps of the process of treating a local portion of conductive element.

[0077] First, the device must be mounted on the conductive element in such a way that the heating section covers the local portion 21 to be treated. Figure 5 shows two non-limiting examples of articulation systems suitable for such mounting on the conductive element 2. Indeed, the device can be in two parts, connected, for example, by a hinge system to allow it to be closed onto the conductive element 2. The heating section 12 can therefore be dimensioned so that it is at least the same length, along the X direction, as the local portion to be treated.

[0078] One method of mounting the device 1 on the conductive element 2 may be as follows: - Opening of two parts 1.1, 1.2 of device 1 relative to each other by pivoting them around an articulation system 15, - Approach the conductive element 2 so as to insert it into the passage 11, - Closure of the two parts 1.1, 1.2 around the conductive element 2.

[0079] A locking system (not shown) may be provided so as to hold the two parts 1.1, 1.2 of device 1 in the closed position around the conductive element 2.

[0080] Fig. 5 thus shows two cross-sectional views 5a and 5b of a device 1 equipped with such an articulation system 15.

[0081] The first view 5a shows a device 1 with a rectangular cross-section, and equipped with a passage also with a rectangular cross-section, particularly suited to handling a busbar-type conductive element 2. The tubular body 1 thus comprises two parts capable of closing onto each other by pivoting around a hinge 15. In this case, in order to accommodate a bar with a rectangular cross-section, the two parts 1.1, 1.2 are of different shapes. In the example shown, one has three sides and thus defines the passage 11 in which the bar can be housed; the other corresponds to a cover, capable of closing the last side of the passage 11.

[0082] The other view 5b shows a device equipped with a passage 11 of circular cross-section, particularly suited to a conductor of the harness type. The principle is equivalent, but differs in that here the two parts 1.1 and 1.2 are permitted to have identical shapes. In the example shown, these are two half-cylinders capable of closing onto each other. The two parts are thus symmetrical along a plane including the elongation direction X of the tubular body. Unlike the case of a busbar, the cylindrical shape of the harness here allows the two half-cylinders to close without difficulty.

[0083] It is understood that the heating element 31 and the cooling system 32 each comprise a first part integrated into part 1.1 and a second part integrated into part 1.2 of the body. For example, if the heating element 31 is a coil, closing the hinge 15 creates an electrical contact between two half-coils. The same applies to the cooling circuit. Appropriate seals or electrical connectors may be provided to ensure continuity between the heating element 31 and the cooling system at the joint.

[0084] Once the device is mounted on the conductive element, the principle of the treatment consists of using the heating section 12 to raise the temperature of the local portion 21 to a temperature sufficient to locally modify the microstructure of the conductive material.

[0085] Indeed, once the device is mounted on the conductive element, the heating element 31 can be controlled to raise the temperature of the heating section 12, which then transmits the heat to the local portion 21 of the conductive element.

[0086] The heating is carried out so that the heating section 12 reaches a setpoint temperature Tf determined according to the following formula:

[0087] [Math 1]:

[0088] ' / — B+i^ / 2 + * m

[0089] Tm being the melting temperature of the conductive material, A and B being linear functions of the equivalent radius R of the passage 11 of the device, the temperature Tf being expressed with a margin of error of + / -5%.

[0090] According to examples, A is equal to a*R+b, with a between 270 and 300, preferably equal to 285, and b between -0.7 and -0.5, preferably equal to -0.6; and / or B is equal to a'*R+b' with a' between 1.0 and 1.2, preferably equal to 1.1 and b' between -0.0020 and -0.0018, preferably equal to -0.0019.

[0091] This formula was determined through the test campaign described below. This formula links the dimensions of the device to the process that should be used to obtain an advantageous crystallographic structure for a conductor to be bent. This formula also shows that the value of Tf will be minimized when E / R is small, and when Le is large; the choice of dimensions therefore directly influences the heating temperature Tf and thus the energy consumption required to process the local portion of the conductor.

[0092] Figure 7 shows point clouds for which the processing provides satisfactory results. Each set of points is given for a specific gauge value. The gauge value is a common unit for sizing a copper wire and can be converted into a conductor radius R according to the following conversion table:

[0093] [Tables 1] Gauge A WG (American Wire Gauge) Diameter (mm) 0000 (4 / 0) 11.7 000 (3 / 0) 10.4 00 (2 / 0) 9.27 0 (1 / 0) 8.25 1 7.35 5 4.62

[0094] Each set of points represented in [Fig.7] gives, for each value of "gauge" tested, the temperature value Tf in ordinate corresponding to a value of Lc / 2 in abscissa.

[0095] The setpoint temperature Tf is thus higher than the melting temperature of the material constituting the conductor so that the local portion 21 liquefies at least partially during heating.

[0096] Indeed, the heating section 12 can also insulate the local portion 21, so that it may be necessary to heat to a temperature higher than the melting temperature of the material to obtain a change of state, at least partial, of the conductive element.

[0097] According to examples, the local portion 21 of the conducting element can be brought to a totally liquid state, or to a pasty state considered partially liquid.

[0098] The heating element 31 is controlled to maintain the heating section 12 at the setpoint temperature Tf for a predetermined heating period. The heating period can be selected between 9 and 11 minutes. In one example, the heating period is set to 10 minutes. In another variant, the heating period can be determined empirically, for example, based on the conductor gauge, the objective being to ensure heat supply to a significant area of ​​the local portion. Furthermore, the heating period can be inversely proportional to the difference between Tf and Tm: if the heating temperature is close to the melting temperature, a longer heating period will be required compared to a heating temperature that is significantly different from the melting temperature.

[0099] According to an improvement, the passage 11 can be configured to conform to the shape of the conductive element 2, so that the internal surface 111 delimiting the passage 11 is in contact with the conductive element 2 when the device is mounted. This means that the dimensions of the passage 11 can be chosen to be identical to those of the conductive element. For example, in the case of a harness with a circular cross-section, a circular passage with a radius R substantially identical to that of the harness will be chosen. In this way, heat exchange between the heating and cooling sections and the conductive element is facilitated. Indeed, the presence of an air gap between the device and the conductive element could negatively impact heat exchange.

[0100] The device 1 is specifically designed to remain in a fixed position on the conductive element throughout the heating phase. Indeed, the heating section is designed to cover entirely and exclusively the local portion 21 to be treated, so that that the treatment can be carried out without any relative movement between the local portion of the conductive element 2 and the device 1 being necessary.

[0101] In addition, the step of maintaining the setpoint temperature Tf during a determined heating period is accompanied by maintaining the device 1 on the conductive element 2 in a position, for example axial along X, and / or rotational around X, constant.

[0102] According to examples, the internal surface 111 of the passage 11 may include a surface treatment aimed at limiting the risk of the device 1 sliding along the conductive element 2.

[0103] According to one example, the passage 11 is designed to be mounted with a slight press fit on the conductive element. For this purpose, the dimension of the passage 11 can be chosen to be slightly smaller than the dimension of the conductor. Mounting the device 1 thus prevents any slippage along the conductive element without additional fastening. Other mounting mechanisms known to those skilled in the art for preventing any relative movement between the device and the conductive element can be considered: the use of clamping rings, stops, etc.

[0104] Advantageously, the tight mounting of the device on the conductive element can also prevent material from the local portion, which can be brought to a liquid state, from escaping out of the device.

[0105] Once the heating period is over, the heating is stopped. The device 1 is then held in place so that the cooling sections 13, 14, in cooperation with the cooling system 32, remove the heat and cool the local portion 21 of the conductive element 2 so that it returns to ambient temperature and solidifies again.

[0106] One advantage of the device according to this disclosure may be that, solely due to its sizing and design, it is possible to eliminate the need for temperature control during cooling. Indeed, the design of the device may be sufficient to "adjust" the thermal inertias, allowing this to occur "naturally".

[0107] With reference to [Fig. 6], the particular arrangement of the cooling sections 13, 14 on either side of the heating section 12 allows for gradual cooling and the formation of "domed" solidification fronts 23 (in the presence of menisci) towards the interior of the local portion 21. These domed fronts 23 promote the local formation of crystals oriented along the X-axis during the solidification of the material in the treated local area 21. Indeed, the "domed" shape of the solidification fronts can be achieved by having significant thermal inertia on the heating section 12 and localized cooling at its ends: such a configuration allows The process involves keeping the core of the conductive element molten or in a pasty state and progressively solidifying it by dissipating the heat flow primarily through the ends of the heating section 12. The edges of the solidification fronts, located closer to the cooling sections 13 and 14, are therefore solidified before the core of the conductive element. This results in a "domed" shape of the solidification fronts, which may be concave as they curve back towards the local portion 21.

[0108] The inventors have determined that these solidification fronts 23 form when the device exhibits at least one of the following criteria:

[0109] [Math.2] LC<^R

[0110] [Math.3] 0.001m <E< 0,01m [YES] [Math.4] Lf > 0.01m

[0112] According to examples, the device simultaneously meets each of these three criteria.

[0113] Reference is now made to Figures 8, 9 and 10, which illustrate by way of example the type of microstructure that can be obtained by this treatment process.

[0114] Figure 8 represents the conductor after treatment and identifies two planes, PI and P2. Plane PI intersects the conductive element (here, by way of non-limiting example, a harness) at the treated local portion 21, which extends over a length LL. Plane P2, on the other hand, intersects the conductive element 2 outside the local portion 21, at a portion that has not been treated by the treatment process described above. Planes PI and P2 can typically be perpendicular to the elongation direction X of the conductor.

[0115] As illustrated in [Fig. 9], the process according to this disclosure makes it possible to obtain a modified microstructure on the local portion 21. Figure 9a schematically represents the microstructure in the PI plane of [Fig. 8], and Figure 9b represents the microstructure in the P2 plane of [Fig. 8]. In the example shown, the microstructure of the treated local portion 21 comprises large grains 211, here only 5 grains (view a). It is also possible, using the process described above, to obtain a single-crystal structure. In comparison, the conducting element 2 has a polycrystalline microstructure on its untreated portions, which, as an example here, comprises approximately 40 crystals (in view b). [Fig. 8] and the two views 9a and 9b represent examples of cross-sections highlighting the number of grains per conductor section.

[0116] In general, the process according to this disclosure can make it possible to obtain, on the treated local portion 21, a number of grains of up to 20 grains per conductor cross-section considered at any point perpendicular to the elongation direction X of the length of the local portion 21 (the cross-section being obtained for example in the manner of [Fig.8]), an untreated portion 22 of the same conductor comprising at least 21 grains per conductor cross-section considered at any point perpendicular to the elongation direction X.

[0117] According to examples, the conducting element may have a diameter between 4 and 12 mm.

[0118] The microstructure of the local portion 21 is shown in perspective and in transparency in [Fig. 10]. After treatment, the crystals are not only larger than originally, but are also oriented along the elongation direction X of the conducting element 2. Such large grains can extend over a major part of the length of the local portion. This preferred grain orientation is a direct result of using the device described above (one heating section and two cooling sections) and raising the temperature to the temperature Tf, which is a function of the device geometry.

[0119] In a randomly oriented polycrystalline structure, as seen in Figure 9b, for example, grain boundaries can extend transversely to the elongation direction of the conductor and impede electron flow, reducing their mobility and decreasing the electrical conductivity of the material. In an oriented structure such as that obtained by the treatment, the crystals are aligned coherently and parallel to the elongation direction of the conductor, allowing the discontinuities of the grain boundaries not to (or to a lesser extent) impede electron flow. This thus reduces electrical resistance and improves conductivity. Such grain boundaries 212 separating the large grains 211, and their orientation, are particularly visible in [Fig. 10].

[0120] Furthermore, the microstructure modification obtained by the treatment described above also allows for significant changes in the mechanical properties of the conductor. Indeed, the monocrystalline or coarse-grained oriented portion will be less resistant to bending and will be more easily pliable. The inventors conducted comparative tests on two copper bars: the first, polycrystalline, the second, monocrystalline:

[0121] [Tables2] Fmax Deflection (dL) for Fmax Diameter of water bar Cross-section of water bar (MPa) (mm) (mm) (mm2) Cu polycrystalline linear 296.39 0.44 11.98 112.72 Cu monocrystalline linear 132.45 19.65 12.31 119.02

[0122] In particular, this comparative test shows that the deflection obtained for the treated single-crystal portion is more than forty times greater, demonstrating that the conductor is more easily bendable in this area. In other words, less force is required to bend the conductor, and it is not damaged by this bending. On the other hand, the maximum permissible force Fmax, determined based on the mechanical strength of the bar, is greatly reduced following the treatment. This is one of the reasons why manufacturing processes known in the prior art are unsatisfactory: they do not allow the conductor to be treated over a localized portion of its length, but only to be manufactured in its entirety with a specific microstructure. The resulting conductive element is therefore subject to significant deformation, even in the portions that are not intended to be bent.The process described above therefore presents the best compromise for obtaining a good conductor (limiting losses due to Joule effect) and whose overall mechanical strength remains sufficient.

Claims

1.

2. Demands A process for treating a local portion (21) of an electrically conductive element (2) made of a conductive material, the process comprising the steps of: - mounting a device (1) around the conducting element (2), the device comprising a tubular body of axis X and radial thickness E, having a passage of equivalent radius R configured to accommodate the conducting element, the device comprising a heating section (12) being axially adjacent, at its ends, to two respective cooling sections (13, 14), the heating section (12) extending axially over a length Le and the two cooling sections (13, 14) each extending axially over a length Lf, the heating section (12) comprising a heating element (31), the cooling sections (13, 14) each comprising a cooling system (32), the device being mounted so that the heating section (12) covers said local portion (21) of the conducting element (2), - heat said heating section (12) by the heating element (31) until it reaches a setpoint temperature determined according to the following formula: rf, 4, Jn(l+f), Tm being the melting temperature of the material B+l. / , * m conductor, A and B being linear functions of R, the temperature Tf being expressed with a margin of error of + / - 5%, - maintain said setpoint temperature Tf for a determined heating period, - stop heating the heating element, and - maintain in place the device (1) so that the cooling portions (13, 14) cool the local portion of the conductive element so that it returns to ambient temperature. A method according to claim 1 wherein A is equal to a*R+b, with a between 270 and 300, preferably equal to 285, and b between between -0.7 and -0.5, preferably equal to -0.6; and / or B equals a'*R +b' with a' between 1.0 and 1.2, preferably equal to 1.1 and b' between -0.0020 and -0.0018, preferably equal to -0.0019.

3. A method according to any one of claims 1 to 2, wherein the temperature maintenance step extends for a period of between 8 and 12 minutes, preferably 10 minutes.

4. Device (1) capable of carrying out the treatment process according to any one of the preceding claims, the device (1) comprising a tubular body of axis X, having a passage (11) configured to accommodate the conductive element (2), the device comprising a heating section (12) being axially adjacent, at its ends, to two respective cooling sections (13, 14), the heating section (12) comprising a heating element (31), the cooling sections (13, 14) comprising a cooling system (32).

5. Device (1) according to the preceding claim, wherein the tubular body has a radial thickness E, the passage has an equivalent radius R, the heating section (12) extends axially over a length Le and the two cooling sections (13, 14) each extend axially over a length Lf, the device being dimensioned such that at least one of the following three criteria is met: LC < 4R, 0.001 m <E<0,01m ; - et que Lf > 0.0Iwî.

6. Device according to any one of claims 4 and 5, the tubular body or each of the sections comprising two half-cylinders (1.1, 1.2) linked together by a hinge system (15) such that the device (1) is configured to close around a local portion (21) of said conductive element (2).

7. Device according to any one of claims 4 to 6, wherein the heating element (31) and / or the cooling system (32) are located on a radially external side respectively of the heating section (12) and the cooling sections (13, 14).

8. Device according to any one of claims 4 to 7, wherein the heating element (31) comprises one of: a coil, a resistor.

9. Device according to any one of claims 4 to 8, wherein the heating section (12) comprises a material from: alumina, ceramic.

10. Device according to any one of claims 4 to 9, wherein the cooling system (32) includes a water circulation.

11. Device according to any one of claims 4 to 10, wherein each cooling section (13, 14) comprises steel.

12. Device according to any one of claims 4 to 11, wherein the heating section (12) is a first heating section (12.1) and the two cooling sections constitute a first cooling section (13.1) and a second cooling section (13.2), the device further comprising a second heating section (12.1) being axially adjacent, at its ends, to the second cooling section (13.2) and to a third cooling section (13.3) respectively.

13. Device according to the preceding claim, wherein the second cooling section (13.2) extends axially over a length Lf2 dimensioned such that Lf2> 0.03 / W.

14. Electrically conductive element (2) comprising at least one local portion (21) treated by the treatment process according to any one of claims 1 to 3.

15. Conducting element (2) extending over a length L along an elongation direction and comprising: - a treated local portion (21) comprising a first single-crystal or coarse-grained microstructure in which the grain(s) (211) are oriented along the elongation direction X of the conducting element, the local portion (21) comprising a maximum of 20 grains per conductor cross-section considered at any point perpendicular to the elongation direction X of the length of the local portion (21), - an untreated portion (22) distinct from the treated portion (21) and comprising a polycrystalline microstructure in which the grains are randomly oriented, the untreated portion (22) comprising at least 21 grains per conductor cross-section considered at any point perpendicular to the elongation direction X of the length of the untreated portion (22).

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